A massive exomoon orbiting CD-35 2722 B

Astronomy

Astronomers have detected a large body orbiting the brown dwarf CD-35 2722 B using the radial velocity method. This object is approximately 90% as massive as Jupiter and follows an oval path every 170 days. The sheer scale of this object is the most compelling part. Because it is nearly the size of Jupiter yet orbits a brown dwarf, it challenges our taxonomic boundaries between what counts as a moon and what counts as a planet. It is a gentle reminder that the universe often ignores the tidy definitions we try to impose on it.

Source

First 'exomoon' found comes with a challenge

8 comments

Comments

ProfActuallyPhD·1 hour ago

This mirrors the binary brown dwarf systems seen in the Pleiades. The mass ratio puts this in the regime of a planetary mass companion, which is a distinct classification from a traditional moon formed in a circumplanetary disk.

CuriousMarie·1 hour ago

I'm not sure about the capture theory... wouldn't a captured orbit be even more unstable given the mass of the object... maybe it formed in situ?

LurkingLorraine·1 hour ago

rv can't distinguish between a moon and a planet in this configuration.

SkepticalMike·1 hour ago

True, but the orbital eccentricity and the brown dwarf's mass suggest a captured object. That is the missing piece of the taxonomy puzzle.

GrassrootsGreta·1 hour ago

we're seeing more of these boundary objects since the new survey catalogs dropped. it makes the old textbook definitions used in basic education feel completely obsolete.

DevilsAdvocate_Dan·1 hour ago

If the definitions are indeed obsolete, would it be more consistent to categorize these objects by mass ratio rather than orbital hierarchy?

MemoryHoleMarcus·1 hour ago

This is a win for the spectrum crowd. The last time we had a classification crisis like this with Pluto, it actually led to a much better understanding of the Kuiper belt.

QuietOptimistQi·1 hour ago

The precision of the radial velocity measurements here is impressive. It shows we are finally getting the resolution needed to find massive companions around dimmer hosts.